In a physical quantity sensor, a semiconductor chip having a sensing portion for detecting a physical quantity such as angular speed, acceleration and pressure is electrically connected to a circuit chip. A method for connecting the semiconductor chip and the circuit chip is disclosed in, for example, JP-A-H11-8270. The method is to connect them by a flip-chip bonding method.
Specifically, the semiconductor chip has a pad made of aluminum disposed on one side of the chip and a first bump made of gold and disposed on a surface of the pad. The circuit chip has a second bump made of gold and disposed on one side of the chip. The semiconductor chip is bonded to the circuit chip in such a manner that the first bump faces and contacts the second bump. Thus, the sensor has a gap between the semiconductor chip and the circuit chip. Here, the flip-chip bonding process is performed by an ultrasonic bonding method.
In the above method, when the first bump is bonded to the second bump, an extra object may be generated, and attach to the sensing portion of the semiconductor chip. The sensing portion includes a movable portion, which is exposed on one side of the chip. Therefore, if the extra object adheres to the sensing portion, performance of the sensing portion is reduced.
To protect the sensing portion of the semiconductor chip, a resin film having adhesiveness covers the sensing portion. The resin film includes a groove facing the sensing portion so that the resin film does not contact the sensing portion. Thus, even when the resin film is attached to the semiconductor chip, the sensing portion does not contact the resin film.
When the semiconductor chip is bonded to the circuit chip through the resin film by the flip-chip bonding method, the resin film is heated in order to improve adhesiveness thereof, and then, the semiconductor chip is bonded to the circuit chip so that they are integrated. In this case, the bump of the semiconductor chip or the bump of the circuit chip pushes aside the resin film so that they are bonded directly.
However, since the resin film is heated, the resin film may be softened. Further, a compression stress is generated when the semiconductor chip is bonded to the circuit chip. Accordingly, the resin film may contact the sensing portion. When the resin film contacts the sensing portion, the performance of the sensing portion is reduced. Further, the stress from the resin film, which is expanded by heat, may be applied to the bump, so that the bonding strength between the bumps is reduced by stress application.
It is required for a sensor having a semiconductor chip and a circuit chip to prevent a resin film from adhering to a sensing portion of the semiconductor chip and to improve bonding strength between the semiconductor chip and the circuit chip.